glh.MeshBuffer: Merge render code for Render and RenderItem into a single internal method. This removes a fair bit of code duplication.
glh.MeshBuffer: Merge render code for Render and RenderItem into
a single internal method. This removes a fair bit of code
duplication.

Fixes render() to always enable the client state for vertex arrays.
This should not be conditional, regardless of whether we have
actual vertices or not.

go-gl-legacy/glh